Syria is "rapidly spinning out of control," is the nightmarish assessment of the usually sober and understated U.S. Defence Secretary Leon Panetta.
As fighting rages, no one knows what's happened to outlawed stockpiles of deadly Sarin nerve gas and other chemical weapons. Meanwhile, President Bashar al-Assad, the ophthalmologist turned brutal dictator, has gone missing and jihadists may have hijacked a once-secular, pro-democracy uprising.
Collapse of the Syrian regime seems imminent after four decades of iron-fisted, albeit secular, rule that imposed order over sectarian fault lines and it could set off a powder keg of ethnic and religious hatreds. Worse, a collapse in Syria in the heart of the Middle East could ignite a wider war.
In Washington, Moscow and Jerusalem, planners are grappling with a fast-moving set of uncertain – but mostly dire – scenarios.
"It's getting very, very messy," Jordan's King Abdullah warned hours after an assassination strike Wednesday ripped through a meeting of Mr. al-Assad's inner circle at a war cabinet meeting. While Mr. al-Assad's whereabouts remain unknown, the bomb all-but-decapitated the regime, killing Defence Minister Daoud Rajiha (the most senior Christian) and Assef Shawkat, a ruthless military commander married to the president's older sister. Others, including Interior Minister Mohammed al-Shaar, were wounded.
"There is no coming back from the abyss," warned the Jordanian leader, who, like all of the region's unelected rulers is also grappling with the sweeping changes of the Arab Spring. But Syria, with its delicate mix of Arab and Kurd, Christian and Druze, Alawite and Sunni, poses perhaps the Arab world's most volatile and dangerous mix.
"If it breaks down, if civil order breaks down to the point of no return, then it'll take years to fix Syria," King Abdullah warned.
As that collapse of the Assad regime suddenly seemed an imminent possibility, senior Obama administration officials, including military planners, were scrambling to work up contingency plans for worst-case scenarios.
Unlike Egypt, where close military ties gave Washington crucial leverage over the ouster of President Hosni Mubarak or Libya, where the American, Canadian and other allied warplanes allowed western powers to dictate the pace of the war that ousted Col. Moammar Gadhafi, events in Syria are mostly beyond outside influence.
Aside from Russia and Iran, both still loyally propping up the Assad regime, few countries, including the United States, hold much sway in Damascus nor with the rabble of rebel forces, some of whom are evidently Islamic extremists.
Among the nightmare scenarios: that al-Qaeda or other Islamic jihadists could seize Syria's sizeable stocks of chemical weapons, including deadly Sarin and mustard gases. Portable and deadly, they would make perfect terrorist weapons.
According to the New York Times, Pentagon officials were huddling with Israeli commanders to consider the merits of air strikes to destroy Syria's aresenal of chemical weapons.
Aside from grave risk that any outside air attack could ignite a full-blown regional war, there is considerable danger of setting off an uncontrolled release of deadly chemical weapons attempting to destroy stockpiles by bombing.
Officially, the Obama administration was only talking tough about the Assad regime's obligations for its weapons of mass destruction. "The Syrian government has a responsibility to safeguard its stockpiles of chemical weapons, and the international community will hold accountable any Syrian official who fails to meet that obligation," said President Barack Obama's spokesman Jay Carney.
But Mr. Obama also called Russian President Vladimir Putin in the hours after the deadly bombing in the heart of Damascus, apparently seeking some common ground as the world's sole remaining superpower and Syria's most powerful ally gird for the uncertainties of a collapse.
Even if Mr. Assad rallies his remaining loyalists and the still-powerful Syrian military beats back the latest assaults that have brought the civil war to the heart of the capital, few observers believe the regime can survive. An orderly transition now seems a faint hope; minimizing the potentially catastrophic consequences of collapse is the new imperative.